SAE behaviour

I just added a new batch of SAEs to my office tank. I'll move some off to
the Plant tank in a few weeks and leave a few behind. I can't seem to keep
Otos in the Plant tank, they just seem to disappear. Likely the Barbs are
the problem, but they don't seem to bother the Tetras.

The new SAEs seem to be doing a lot of "tail standing", swimming vertically
up and down the glass. I gather this is some kind of food search? But they
are ignoring the Green Dust Algae on the front glass, swimming right by it.

Also how few SAEs can I leave in a group. The office tank is only ten
gallons, so I did not want to leave more than 1 or 2 SAEs. Maybe I'll move
all the SAEs and leave the Otos behind, but that would give me six SAEs in
the 55 gallon. I KNOW, a BIGGER office tank. LOL.